Comprehensive Chromosome Screening (CCS) is a new laboratory technology which provides critical information about embryos prior to their transfer into the uterus. Chromosomes are arrangements of DNA, the road map to all cells in the body. Errors in formation of chromosomes are the biological explanation for many forms of infertility and poor reproductive outcomes such as miscarriage or the birth of child with major developmental problems.

Why is it “new” ?

Prior to the maturation of the CCS technology, efforts to report on the chromosomal content of embryos were met with several difficulties. One of the major limitations was that information was only gained on a relative few of the 23 different pairs of chromosomes that each cell possesses. This incomplete information translated into suboptimal clinical use of this test. However, with analysis of all 23 pairs of chromosomes (thus the term comprehensive) we are able to make more confident decisions about the health of the embryo.

How CCS works

CCS starts with a sampling of the embryo on its 5th day of life (“blastocyst” stage). The cells that are biopsied are destined to become the placenta, not the baby. This procedure is akin to a chorionic villus sampling or amniocentesis which is performed during pregnancy and, although data is still being acquired, appears to be very safe. Tissue is submitted to a specialized laboratory which, with blood samples from the parents, analyzes the chromosome content of each individual embryo. A report is generated which provides a high level of confidence as to which embryos are chromosomally normal.

When to consider CCS

CCS has an expanding array of indications including:

• Unexplained infertility
• Repeat implantation failure
• Prior miscarriage or recurrent pregnancy loss
• Desire for single embryo transfer (limiting multiple gestation risk)
• Gender selection
• In conjunction with PGD (preimplantation genetic diagnosis; detection of known gene mutations)